1. Field
The present invention relates to an apparatus and method for sensing a change in a thickness of a strip of material from a desired thickness. More particularly, the present invention relates to a sensor using fiber optic light detection to determine a change in thickness of a material.
2. Related Art
Composite tape strips are used to form composite parts, such as those used in the manufacture of aircrafts. In a lay-up process, strips of the composite tape are applied to a surface, layered, and then cured by pressure and heat to form a strong, light-weight composite part.
During the production of composite tape or tow, flawed portions of the tow may be cut out, resulting in two cut ends which may be spliced together. This increases the thickness of the composite tape in the location where the strips have been spliced. Depending on the product being manufactured, limits may be placed on the number of splices within a given area and/or the minimum spacing of splices along any singular composite tow.
When a splice is inserted into the composite tow, three light colored stripes are painted in the region of the splice. Inspectors may look over the surface where the tows have been laid and look for these stripes, but doing so is difficult because the stripes are often hard to see. Automatic ways of detecting the stripes have proven error prone due to the variation of stripe quality. Additionally, splices made during the fiber placement process are sometimes not marked at all and therefore nearly impossible to detect.
Accordingly, there is a need for an improved splice detector that overcomes the limitations of the prior art.